R2 signalling:It is called register signalling based on CAS signalling in which signalling & traffic alwaya take same path in network.Example:in 20 E1s ,16 channel no of each E1 is kept for signalling only.
SS7/CCS signalling:Signaling & traffic do take same path .In 20 E1s, 10 Timeslot of one or two PCMs are reserved for signalling for all PCMs.
Regards,
Prasanta Kumar Bastia
Senior Engineer Telecom